Force limiting retractor with matching belt webbing

ABSTRACT

Safety belt winder with a locking system for the belt shaft as support for the belt webbing wound upon said belt shaft, which reacts to the vehicle or the safety belt. The safety belt winder has an integrated force limiting device for the safety belt force occurring in the belt webbing on locking the safety belt winder. The belt webbing has a breaking strain of less than 20 kN, with less than 35 warp threads per 10 mm, running in the longitudinal direction thereof and the twill-woven weft yarn is in the form of monofilament threads.

DESCRIPTION

[0001] The invention relates to a safety belt roll-up mechanism having ablocking system that is sensitive to or reacts to a vehicle and/or abelt strap, the blocking system being for the belt shaft as a support ofa belt strap wound onto the belt shaft. With such belt roll-upmechanisms it is known, for example from WO 96/32303, to integrate aforce-limiting device in order to limit the belt strap forces that occurdue to blocking of the safety belt roll-up mechanism that is initiatedwhen dangerous situations occur, and which endanger the strapped-inoccupants. Up to now, the use of a force limitation within a safety beltroll-up mechanism has not led to an adaptation of the design of the beltstrap to the force conditions that have changed due to the use of aforce limiting device in the safety belt roll-up mechanism; theinvention therefore proposes in detail, with regard to the design of thebelt strap, that the belt strap, which has a breaking load of less than20 kN, has fewer than 35 warp threads per 10 mm of belt strap width,with the warp threads extending in the longitudinal direction of thebelt strap, and the twill-woven weft threads are embodied asmonofilament threads.

[0002] Thus, to the extent that the use of a force limiting device in asafety belt roll-up mechanism enables the belt strap force that occursin the region of the blocked belt roll-up mechanism to be limited ineach buckled or strapped-in position, and in all cases when a loadoccurs, it is inventively proposed to significantly reduce the breakingload of the belt strap in comparison with conventional belt straps. Thisreduction of the breaking load makes it possible, pursuant to theinvention, to reduce the number of the warp threads, which extend in thelongitudinal direction of the belt strap, by about 40% relative toconventional belt straps, to fewer than 35 warp threads per 10 mm ofbelt strap width. This lower number of warp threads has the advantagethat a lower longitudinal stiffness of the belt strap is establishedrelative to the conventional belt strap; furthermore, the weight of thebelt strap is reduced due to the reduced material use, and finally therealso results a lower belt strap thickness due to the fact that themonofilament weft threads, which, despite the reduced number of warpthreads, effect an adequate transverse rigidity, are during the weavingdisposed between the warp threads, which extend at a greater spacingrelative to one another. All three factors together lead to animprovement of the placement and removal comfort, as well as of thewearing comfort, of the belt strap.

[0003] From a technical standpoint, the reduced belt strap thicknessleads to a smaller diameter of the belt shaft, so that the installationdimensions of a correspondingly equipped safety belt roll-up mechanismare reduced. At the same time, the feed spool effect, which occursduring loading of the belt strap wound upon the belt shaft, is alsolower, and hence an uncontrolled preliminary movement of the strapped-inoccupant is reduced.

[0004] Finally, the invention also has economical advantages; forexample, due to the lower material usage, and the weaving speed, whichis possibly increased due to the lower number of warp threads, themanufacturing expense for weaving the belt strap is reduced. Inaddition, the subsequently necessary finishing of the belt strap fabricby thermo fixing is less expensive, since, for example, a prescribedelongation characteristic no longer has to be set.

[0005] DE 31 13 701 suggests a thinner belt strap in order to therebyreduce the volume and weight of the safety belt roll-up mechanism;however, in so doing it is specifically indicated that the strength ofthe belt strap should be maintained, so that this document provides nosuggestion for achieving the inventive teaching. To the extent that thisdocument might address a conceivable reduction of the number of warpthreads, this conceivable reduction of the number of warp threads iscompensated for by an increase in the number of weft threads.

[0006] In a similar manner, DE 41 04 516 A1 addresses the possibility ofreducing the number of warp threads, however, this reduction is to becompensated for by the use of weft threads that are finished in such away that their extensibility against breaking is significantlyincreased. Since by the use of such specialized weft threads, theservice life of the warp threads is to be increased, the strength of thethus-provided belt strap is maintained in comparison with conventionalbelt straps. In this way, this document also provides no suggestion forachieving the claimed technical teaching.

[0007] The use of monofilament weft threads for setting an adequatetransverse rigidity of a belt strap is, in principle, known from DE 3345 508 A1, however without providing a connection to the number of warpthreads.

[0008] Whereas with conventional belt straps the woven belt strap issubjected to a special finishing, especially by thermo fixing, with theobjective of providing the elongation characteristic of the belt strapsuch that as the loading increases, or after a predetermined loadingstate, the elongation of the belt strap becomes greater in order toenable a preliminary movement of the strapped-in occupant, it isprovided pursuant to one embodiment of the invention that the belt straphave a linear elongation characteristic. In addition to the preliminarymovement of the strapped-in occupant, which is established by the forcelimiting device in the belt roll-up mechanism, this does not lead to aninfluencing of this preliminary movement effect due to an incalculableelongation of the belt strap. To the extent that the elongation of thewoven belt strap can correspond to the elongation of the base materialused for producing the warp threads, there thus results a simplificationduring the finishing of the woven belt strap by thermo fixing.

[0009] For this purpose, it is known from DE 38 41 687 A1 to dispose abelt force limiter in a safety belt system beyond the safety beltroll-up mechanism at the buckle-free end of the lap belt portion,whereby the belt strap that is utilized should have a lower elongationthan conventional belt straps so that the preliminary movement path,which does not occur in a directed manner due to the elongation that isnot foreseeable in the event of load, remains within acceptable limits.

[0010] The features of the subject matter disclosed in the presentspecification, the patent claims, and the abstract can be important notonly individually, but also in any combination with one another forrealizing the various embodiments of the invention.

1. Safety belt roll-up mechanism having a vehicle sensitive and/or beltstrap sensitive blocking system for the belt shaft as a support for abelt strap wound onto the belt shaft, whereby the safety belt roll-upmechanism is provided with an integrated force limiting device for thebelt strap force that occurs in the belt strap during blocking of thesafety belt roll-up mechanism, and whereby the belt strap, which has abreaking load of less than 20 kN has fewer than 35 warp threads per 10mm belt strap width, such warp threads extending in the longitudinaldirection of the belt strap, and the twill-woven weft threads areembodied as monofilament threads.
 2. Safety belt roll-up mechanismaccording to claim 1, characterized in that the woven belt strap has alinear elongation characteristic.
 3. Safety belt roll-up mechanismaccording to claim 1 or 2, characterized in that the elongation of thewoven belt strap corresponds to the elongation of the base materialutilized for the manufacture of the warp threads.
 4. Safety belt roll-upmechanism according to one of the claims 1 to 3, characterized in thatthe base material for the manufacture of the belt strap fabric is apolyester.